Continuous process for preparing aluminum alkyls and linear 1-olefins from internal olefins

ABSTRACT

Linear 1-olefins are continuously prepared from internal olefins by (i) continuously feeding internal olefin, isomerization catalyst and tri-lower alkyl aluminum to a reaction zone so as to cause the internal olefin to isomerize to 1-olefins which displace the lower alkyl groups to form a trialkyl aluminum compound in which at least one of the alkyl groups is a linear alkyl derived from the 1-olefin, (ii) continuously removing trialkylaluminum compound from the reaction zone and, thereafter (iii) reacting the trialkyl aluminum compound with a 1-olefin so as to displace the linear alkyl from the trialkyl aluminum compound, thereby forming a linear 1-olefin product which is substantially free of internal olefins.

This application is a division of application Ser. No. 07/739,654, filedAug. 2, 1991, now U.S. Pat. No. 5,191,145, which is acontinuation-in-part of application Ser. No. 674,104, filed Mar. 25,1991 now U.S. Pat. No. 5,124,465 which is incorporated herein byreference.

BACKGROUND

This invention relates generally to a process for the isomerization ofinternal olefins and more specifically to a continuous process for thepreparation of aluminum alkyls from internal olefins such as mixedinternal hexenes or mixed internal octenes. Linear 1-olefins derivedfrom the internal olefins can be recovered from the aluminum alkyls byback-displacement.

Linear 1-olefin compounds such as 1-hexene are useful comonomers withlower olefins to prepare polymers having improved physical properties.The 1-hexene is normally produced as a co-product of olefin productionby a variety of well-known processes such as the ethylene chain growthprocess in which ethylene reacts with lower aluminum alkyls to formhigher alkyl aluminum compounds. The higher, C₄ to C₃₀ or above, alkylgroups are then displaced from the aluminum by, for example, ethylene or1-butene to form C₄ to C₃₀ linear 1-olefins which can be separated andrecovered. Increasing demand for 1-hexene has produced a need forpreparing it as the primary product. Processes for preparing olefinssuch as by the dehydrogenation of paraffins or the metathesis of otherolefins produce mainly internal olefin products which must then beconverted to 1-olefins. Asinger et al. U.S. Pat. No. 3,322,806 describethe preparation of primary alcohols from internal olefins by reacting anon-1-olefin with an aluminum lower alkyl in the presence of catalystswhich are compounds of zirconium, uranium, vanadium, chromium, thorium,tungsten, and titanium. The catalyst is believed to promote theconversion of internal olefins to 1-olefins which displace the loweralkyl groups of the aluminum alkyl. The aluminum alkyl is then convertedto a primary alcohol by oxidation and hydrolysis. Asinger et al. alsodisclose such an isomerization/displacement process to prepared alcoholsin Chemische Berichte 97, pages 2515-2520 (1964). They reported thatnickel compounds were inactive. Later, the thesis of Rainer Oberghaus,Technishen Hochschulle, Aachen, (1969) reported a 55 percent yield of a1-alcohol from i-Bu₂ AlR formed by reacting internal olefin andtriisobutylaluminum using a nickel(II) acetylacetonate catalyst.

BRIEF SUMMARY

In accordance with this invention there is provided a continuous processfor preparing an alkyl aluminum compound from an internal olefin, saidprocessing comprising:

(a) continuously feeding (i) a linear internal olefin containing 4 toabout 30 carbon atoms or a mixture of such internal olefins, (ii) atrialkylaluminum, the mole ratio of said linear internal olefins to saidtrialkyl aluminum being about 1 to 50:1, and (iii) a catalytic amount ofan isomerization catalyst to a reaction zone so as to isomerize theinternal olefinic double bond to form at least some linear 1-olefinwhich displaces alkyl groups from said trialkyl aluminum and forms analkyl aluminum compound wherein at least one of the alkyl groups boundto aluminum is a linear alkyl derived from said linear 1-olefin,

(b) continuously removing olefin formed by the displaced alkyl groupsand reaction mixture containing said alkyl aluminum compound from thereaction zone.

In another aspect of the invention there is provided a continuousprocess for making a 1-olefin compound from an internal olefin, saidprocess comprising:

(a) continuously introducing a linear internal olefin containing 4 toabout 30 carbon atoms, or a mixture of such internal olefins, and atrialkyl aluminum, in a mole ratio of linear internal olefin to trialkylaluminum of about 1 to 50:1, into a reaction zone in the presence of acatalytic amount of an isomerization catalyst so as to (i) causeisomerization of the internal olefinic double bond to form at least somelinear 1-olefin and to (ii) cause the linear 1-olefin so formed todisplace alkyl groups from said trialkyl aluminum and form an alkylaluminum compound, wherein at least one of the alkyl groups bound toaluminum is a linear alkyl group derived from said linear 1-olefin, anddisplaced olefin corresponding to said displaced alkyl groups,

(b) continuously removing said displaced olefin and reaction mixturecontaining said alkyl aluminum compound from said reaction zone, and

(c) reacting said alkyl aluminum compound with a 1-olefin in adisplacement zone so as to displace said linear alkyl from said alkylaluminum compound and form a free linear 1-olefin compound.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic flow diagram illustrating a multi-reactorembodiment of the continuous process of the invention for preparingaluminum alkyls.

FIG. 2 is a schematic flow diagram illustrating an embodiment of acontinuous back-displacement step of the process of the invention.

DETAILED DESCRIPTION

The internal olefins which are isomerized in accordance with thisinvention contain from 4 to about 30 carbon atoms, preferably 4 to 18carbon atoms and can include mixtures of such olefins. Such internalolefins can be obtained from a number of sources as known in the art.For example, by the dehydration of alcohols or alcohol mixtures, by themetathesis or disproportionation of olefins such as n-butenes to formethylene, propylene, 3-hexene and 2-pentene, or by the dehydrogenationof C₄ -C₃₀ normal paraffins. Suitable internal olefins include, forexample, cis and trans-2-hexene, cis and trans-3-hexene, mixed internalhexenes, mixed internal dodecenes, mixed internal octadecenes and thelike.

The alkyl aluminum compounds for the isomerization/displacement processhave alkyl groups which, preferably, contain fewer carbons than thepredominant carbon number of the internal olefins. In any event, thedisplaced olefin from the alkyl-aluminum compound should usually have aboiling point below the isomerized olefin because removal of thedisplaced olefin drives the reaction. However, it is also possible thatthe displaced olefin can be a vinylidene olefin, in which casethermodynamic equilibria rather than removal of the olefin can drive thereaction. Suitable alkyl aluminum compounds which contain alkyl groupshaving from 2 to about 20 carbon atoms, preferably 2 to 12 carbon atoms,include, for example, triethylaluminum, tri-n-propylaluminum,tri-n-butylaluminum, triisobutylaluminum, trineohexylaluminum,tri-n-octylaluminum, tri-n-dodecylaluminum, tri-n-octadecylaluminum andthe like. Preferred compounds are straight chain alkyl compounds andespecially those where the alkyl group does not isomerize upondisplacement such as tri-n-propyl aluminum such that the displacedolefin can be easily recycled. Low hydride content aluminum alkylcompounds (less than about 1.0 weight percent and preferably less thanabout 0.1 weight percent) are required to achieve good yields when usingnickel catalysts, because the presence of aluminum hydride impuritiesrapidly deactivates the catalyst. The AlH₃ or R₂ AlH content can bereduced by contacting the aluminum alkyl with a 1-olefin such aspropylene.

Suitable catalysts for isomerization of the internal olefins include,for example, alkali metals such Na or Li on Al₂ O₃ ; Pd, Ni, or Pt oninert supports such as carbon; La on SiO₂ --Al₂ O₃ ; cobalthalide-ligand complexes, e.g. CoBr₂ ·2P(cyclohexyl)₃, metal oxides,metal amides, and the like. Preferred catalysts are those which catalyzeboth isomerization and displacement, for example, titanium and zirconiumcompounds such as Ti(OBu)₄ and Zr(Obu)₄, and the like. Especiallypreferred are nickel-containing compounds which are effectiveisomerization/displacement catalysts to provide yields of aluminumalkyls from internal olefins of about 60 to 90 percent or more. Suchnickel compounds include, for example, nickel(II) salts; nickel(II)carboxylates, nickel(II) acetonates and nickel(0) complexes. Examples ofnickel(II) salts include nickel halides, e.g., nickel chloride, nickelbromide, nickel iodide, and their hydrates and the like. Also useful arenickel(II) oxide, nickel(II) hydroxide and the like.

Nickel carboxylates can be represented by the formula: ##STR1## where Ris hydrogen or C₁ -C₁₆ alkyl; aryl, i.e. phenyl, naphthyl; substitutedaryl, i.e. phenyl and naphthyl substituted with one or more of C₁ -C₁₆alkyl, halogen (Cl, Br, I, F), and/or haloalkyl etc; aralkyl, i.e.benzyl, naphthobenzyl; and substituted arylalkyl where the aryl group issubstituted as described above for substituted aryl, and the like.

Examples of nickel carboxylates include nickel acetate nickel2-ethylhexanoate, nickel octanoate and nickel naphthenate

Nickel acetonates such as acetylacetonate can be represented by theformula: ##STR2## when R is as defined above for the nickelcarboxylates.

The foregoing three types of Ni(II) catalysts are believed to be reducedto Ni(0) compounds in the presence of aluminum alkyl/olefin mixtures andform complexes with the olefin which catalyze theisomerization-displacement reaction.

Examples of Ni(0) complex catalysts include Ni(CO)₄ and Ni(0) olefincomplexes such as nickel bis-1,5-cyclooctadiene (Ni(COD)₂), Ni(C₂ H₄)₃,Ni(norbornene)₃, nickel cyclododecatriene and the like. Other Ni(0)catalysts are nickel compounds which are complexed with a ligand such asa trivalent phosphorous compound. The ligand acts to improve the storagestability of catalysts such as Ni(COD)₂.

Examples of specific ligand compounds include triphenylphosphine,triethylphosphine, triethoxyphosphine, cyclohexylphosphine, P(SiMe₃)₃,and the like.

Examples of specific Ni catalyst-ligand complexes include Ni(PPh₃)₄,Ni(PEt₃)₄ and Ni(P(OEt)₃)₄, each of which are commercially available,and Ni((Me₂ PCH₂)₂)₂, Ni(P(SiMe₃)₃)₃, Ni(COD)₂ ·(cy₂ PCH₂)₂ (wherecy=cyclohexyl), Ni(COD)₂ ·(Me₂ PCH₂)₂, Ni(COD)₂ ·P(O-o-tolyl)₃ withNi(COD)₂ ·Pcy₃ being preferred. The catalyst complexes can be formed bymixing the nickel compound such as Ni(COD)₂ with the desired phosphinein a P/Ni mole ratio of at least 2 for monodentate phosphines at least 1for the bidentate phosphine ligands. Most nickel(0) phosphine ligandsare prepared by reduction of a nickel(II) salt in the presence or aphosphine ligand or by mixing the phosphine with a nickel-olefincomplex.

Mixtures of any of the above mentioned catalysts can also be used.Separate catalysts can be used for isomerization and displacementprovided that they do not interfere with each other. Examples ofdisplacement catalysts include, for example, colloidal Ni, Pt, Co,nickel acetylacetonate, cobalt carboxylates, e.g. cobalt naphthenate orcobalt acetate, nickel carboxylates, e.g. nickel naphthenate and thelike.

The mole ratio of internal olefin to trialkylaluminum can vary andpreferably ranges from about 1-50:1 with 5-20:1 preferred and about 10:1most preferred. Catalytic amounts of nickel catalyst which are effectivein the isomerization/displacement process generally range from about0.01 to 5.0 mole percent of the trialkyl aluminum and preferably about0.02 to 1.0 mole percent.

According to the continuous isomerization/displacement process, thecatalyst is preferably mixed with a portion of the internal olefins toform a first feed solution. The trialkyl aluminum is mixed with a secondportion of the internal olefins to form a second feed solution. The feedrates to the reaction zone are adjusted to provide the desired relativeproportions of catalyst and reactants. Alternatively, the compositionsof the solutions can be selected to provide an approximately equal flowof each feed solution. In order to favor the replacement of the alkylgroups by the isomerized olefins and drive the reaction to highconversion, the displaced alkyl groups in the form of theircorresponding 1-olefins are continuously removed as vapor from thereaction mixture and in one embodiment of the invention are used in therecovery of the desired 1-olefins by back-displacement. Unreactedinternal olefins are separated from the reaction mixture by distillationor vacuum stripping and returned to the isomerization/displacementreaction zone. The stripping process can be carried out in a batch orcontinuous manner. Suitable reaction temperatures range from about -20°to 200° C., preferably about 30° to 100° C. Suitable reaction pressuresrange from about 0 to 100 psia, preferably about 1 to 45 psia andreaction times usually range from about 0.1 to 2 hours. The feed rateand the rate of withdrawal of reaction mixture from the reaction zone aradjusted to provide the desired residence time.

The reaction zone can include one or more individual reactors in series.Catalyst can be added to the first reaction only or, when a plurality ofreactors are used, it can be added to one or more of the additionalreactors. The embodiment of the continuous process invention using aseries of stirred tank reactors with continuous removal of displacedolefin from each reactor has been found to provide lower concentrationsof displaced olefin in the reaction mixture than when a single reactoris used while minimizing back-displacement. This facilitates theconversion of the internal olefin to corresponding n-alkyl groups whichare attached to aluminum.

According to the embodiment of the process of the invention forpreparing linear 1-olefins, the n-alkyl groups from the isomerizedinternal olefins are back-displaced from the trialkyl aluminum compoundsformed in the isomerization/displacement reaction. A suitabledisplacement process is described, for example, in U.S. Pat. No.4,918,254 whose teachings are incorporated herein by reference. Theback-displacement can be carried out in a variety of reactorconfigurations. In a particularly advantageous and novel embodiment, theback-displacement is carried out continuously in a plug flow tubular orpacked column reactor with the product 1-olefin flashed from thereaction mixture at low temperatures in order to minimize isomerization.

As described above, the displaced 1-olefin recovered from theisomerization/displacement reaction can preferably be used as the olefinto back-displace the linear 1-olefin from the aluminum alkyl. Theregenerated trialkyl aluminum can then be recycled to theisomerization/displacement reaction. However, a different olefin can beused for back-displacement and 1-olefins having from 2 to about 18carbon atoms including mixtures thereto are especially suitable. Theback-displacement can be accomplished without a catalyst but ispreferably carried out in the presence of a displacement catalyst. Thenickel catalysts which are carried over from theisomerization/displacement step can be effective to catalyze theback-displacement even though they have become inactive in catalyzingthe isomerization/displacement reaction. The catalysts are apparentlyreactivated in the presence of the displacing olefin and heat, forexample temperatures above about 40° C. and, preferably 40°-80° C. Freshcatalysts can also be added. Preferred catalysts are those which havethe least isomerization activity under the conditions used and include,for example, cobalt carboxylates such as cobalt naphthenate and thelike. Nickel complexes, for example, nickel acetylacetonate, nickelcarboxylates such as nickel naphthenate, nickel octanoate and nickelacetate, are suitable if used in combination with Pb or Pb compounds toprevent isomerization. Although the cobalt catalysts are about 10 timesless active for isomerization than the nickel catalysts, they arepreferably also used in connection with Pb or Pb compounds. Cyclodienesand acetylene hydrocarbons, such as phenyl acetylene, can also be usedin the displacement reaction to suppress isomerization activity andprolong catalyst life. Effective amounts of catalyst depend upon thecatalyst used. Generally amounts of from about 1 to 100 parts permillion based on the weight of the reaction mixture can be used and,preferably about 5-50 ppm. Reaction temperatures of from about -20° to100° C. are suitable for catalyzed displacement. The aluminum alkyl feedto be back-displaced can be treated with a 1-olefin to remove anyaluminum hydride so as to extend catalyst life. Higher temperatures ofabout 300° C. or above may be needed for thermal displacement withoutcatalysts.

The amount of 1-olefin fed to the displacement reaction should be instoichiometric excess over the amount required to replace all alkylgroups. Preferably the amount of 1-olefin should be at least a 200percent excess over the stoichiometric amount required to replace allalkyl groups. Still more preferably the 1-olefin feed should be at leasta 500 percent stoichiometric excess over the trialkyl aluminum feedstream. In this manner, since the displacement reaction is anequilibrium reaction, the alkyl substitution in the trialkyl aluminumproduct will more closely approach the distribution of the 1-olefinfeed.

Both displacement and side reactions (e.g. isomerization, dimerization,chain growth) proceed concurrently. However the displacement reactionrate is much higher than the rate of the side reactions. This permitstermination of the displacement reaction after a time that allows it togo substantially toward the equilibrium conversion and before a time inwhich the side reactions, especially isomerization, become significant.By "significant" is meant the amount of undesired by-products whichwould render the olefin effluent stream unsuitable for its intendedpurpose. In general, the 1-olefin product should contain less than 25weight percent newly formed combined internal, tri-substitutedvinylidene olefins and paraffins. The preferred 1-olefin product is atleast 80 weight percent vinyl 1-olefin and more preferably at least 90weight percent vinyl 1-olefin based on the tri-n-alkylaluminumconverted. The process is capable of making 1-olefin product that isover 97 weight percent vinyl 1-olefin based on tri-n-alkylaluminumconverted.

Since all rates vary with temperature and amount of catalyst, theoptimum time for termination under each specific condition will requirea minimal amount of experimentation. In general when operating at 25°C., the reaction should be terminated after a reaction period of about30 seconds to I hour. A preferred reaction time is 1-20 minutes and mostpreferred 2-5 minutes. At higher temperatures, e.g. 50°-100° C., thepreferred reaction time before side reactions become significant will beshorter.

In using a nickel displacement catalyst, when the displacement hasproceeded to the desired extent, usually close to reaction equilibrium,a catalyst poison can be added in an amount that will deactivate thenickel catalyst and prevent undesirable side reactions. These poisonsinclude lead and copper and compounds thereof. Suitable lead compoundsare lead naphthenate, lead acetylacetonate, lead 2-ethylhexanoate,tetraethyl lead, etc. Suitable copper compounds are copper naphthenate,copper acetylacetonate, cuprous bromide, cuprous 2-ethylhexanoate andthe like. Use of the metals as the catalyst poison requires the metalsto be in very finely divided forms and requires a greater amount of thecatalyst poison. For example, amorphous lead metal is an effectivecatalyst poison at a Pb/Ni atom ratio of about 500. The catalyst poisonswhich are effective at the lowest concentrations have been leadcompounds, e.g. lead naphthenate, lead 2-ethylhexanoate and leadacetylacetonate.

The amount of catalyst poison should be an amount that effectivelyinhibits all undesired side reactions. With lead compounds a lead/nickelatom ratio of 1.0 has been effective and even lower amounts may beeffective. Hence a useful Pb/Ni atom ratio is about 0.5/1.0 to 5.0/1.0.

After the catalyst poison has been added, the trialkyl aluminum productcan be recovered by conventional methods such a distillation. When leadcompounds are used as the poison, nickel and at least part of the leadform a precipitate which can be removed by filtration.

Isomerization during back-displacement can also be suppressed by theaddition of an isomerization suppressing amount, preferably, from about1.0 to 5.0 grams per milligram of nickel in the catalyst, of acyclodiene compound such as a cyclooctadiene, cycloheptatriene or1,3-cyclohexadiene and, preferably 1,5-cyclooctadiene. Although smallamounts of such cyclodienes favor isomerization, the use of at leastabout 1.0 gram of cyclodiene per milligram of nickel in theback-displacement reaction, produces a vinyl olefin product which has areduced isomer impurity content. Unlike lead, the cyclooctadiene can beeasily recovered for reuse. This avoids the need to remove added leadand inactivated nickel catalyst by filtration prior to recycling thealuminum alkyl to the isomerization/displacement reaction. Isomerizationis also suppressed by acetylenic compounds.

In FIG. 1 an embodiment of the process of the invention for continuouslypreparing aluminum alkyls from internal olefins is schematicallyillustrated in which the reaction zone is made up of four stirred tank(back-mix) reactors each of which is equipped with a stirrer,temperature indicator, heater, Vigreux Column and liquid cooledcondenser.

According to the process, a trialkyl aluminum-internal olefin mixture iscontinuously fed from source 10 by duel head peristaltic pump 12 intoreactor 15 through line 14. An internal olefin-catalyst mixture iscontinuously fed from source 11 by pump 12 into reactor 15 through line13. The feed rate of each solution is controlled by adjusting thepumping rates. Reaction mixture from reactor 15 is continuously removedthrough line 24 and introduced into reactor 25. The inlet and outlet ofline 24 are located beneath the liquid level in each reactor. Similarlyreaction mixture from reactor 25 is transferred to the third reactor 35through line 34 and to the fourth reactor 45 through line 44. The liquidtransfer lines are located beneath the liquid level to avoid thetransfer of vapor between reactors so that reflux will occur in eachreactor.

The liquid level in the system is controlled by positive displacementpump 51 which removes reaction product mixture containing the alkylaluminum product through line 52 to holding tank 53. In each reactor,internal olefin is isomerized to 1-olefin which displaces the alkylgroups of the feed alkyl aluminum and releases them as the corresponding1-olefin. This 1-olefin is removed from each reactor as a vapor throughreflux columns 17, 27, 37 and 47 and liquid cooled condensers 19, 29, 3and 49 and collected in line 50 where it is carried by a nitrogen purgeto prevent air from entering the system. The displaced 1-olefin caneither be discharged through a bubbler or collected and fed to theback-displacement process step when it is desired to recover free1-olefin corresponding to the internal olefins from the producttrialkylaluminum. The alkylaluminum product in tank 53 is pumped throughline 54 by positive displacement pump 55 to preheater 56 and then to thetop of Oldershaw Column 57 where unreacted internal hexenes are removedas overheads. The internal hexenes are liquified in condenser 58 andcollected in tank 59 from which they can be returned through line 60 tothe make-up feed for the isomerization/displacement reaction zonethrough line 60. Cyclohexane from supply 61 is pumped to the reboiler 62of Oldershaw Column 57 by peristaltic pump 63 at a rate so as tomaintain the reboiler bottoms at the desired temperature. Theapplication of vacuum, for example from about 10-100 mm Hg, may be usedinstead of an inert volatile chaser (cyclohexane) to maintain thetemperature at the desired levels. The stripped alkyl aluminum productcollects in reboiler 62 and is pumped through line 64 by peristalticpump 65 to stripped alkyl tank 66.

The process for preparing aluminum alkyls in the above system is furtherillustrated by but is not intended to be limited to, the followingexamples.

EXAMPLES 1-3 Preparation of Isomerized Hexenes

Into a 100-gallon Pfaudler glass-lined reactor equipped with an overheadcondenser are added 421 lb. of 1-hexene, 4.21 lb. of tri-n-hexylaluminum, and 38 grams of 8 percent nickel octanoate in mineral spirits.The chemicals are added in an anhydrous and air-free manner and anitrogen blanket is added to the reactor to prevent the entry of air.The reactor was then heated to 60° C. and maintained at that temperaturefor two days.

At the end of two days, the 1-hexene is converted into an equilibriummixture of linear hexenes as evidenced by gas chromatography(approximate composition: 2 percent 1-hexene; 18 percent cis-2-hexene;57 percent trans-2-hexene; 3 percent cis-3-hexene; 20 percenttrans-3-hexene). The reaction mass is then distilled to recover thehexenes overhead. The residual aluminum alkyls and other organicsremaining in the reactor are carefully treated with 2N H₂ SO₄ and thenthe aqueous layer is neutralized and discarded. The remaining organicsin the reactor are incinerated. About 309 lbs. of an equilibrium mixtureof linear hexenes are recovered overhead.

This equilibrium mixture of linear hexenes (henceforth hexenes) is usedas feed for the isomerization-displacement reactions. These hexenes arestored over Zeolite 3A and kept under a nitrogen pad until use.

Treatment of Aluminum Alkyls

Tri-n-propyl aluminum (TNPA) is treated to remove residual hydride.Approximately 100 g of tri-n-propyl aluminum is combined withapproximately 100 g of 1-hexene in a 500-cc round-bottom flask equippedwith a magnetically-coupled stirring bar, heating mantle, and refluxcondenser. The condenser is maintained at about 0° C. with analuminum-alkyl-compatible heat transfer fluid such as a 2 centistokepolyalphaolefin. The contents of the flask are heated to reflux for onehour and then are cooled and vacuum-stripped to remove the 1-hexene.Analysis of the tri-n-propyl aluminum typically showed that it contained5-15 percent hexyl groups following the treatment. This treatedtri-n-propyl aluminum (henceforth, TNPA) is used in theisomerization/-displacement reaction experiments.

The continuous isomerization/displacement process illustrated in FIG. 1is used in preparing tri-n-hexyl aluminum from the isomerized hexenemixture and tri-n-propyl aluminum described above. The reactors are 50cc, magnetically stirred round-bottom flasks equipped with heatingmantles and 12 inch Vigreux Columns. A cold heat-transfer fluidcompatible with aluminum alkyls (e.g. polyalphaolefins) is pumpedthrough the condensers at about 0° C. The apparatus is purged with drynitrogen before operation and during operation there is a cross-purge ofnitrogen to prevent air from entering the apparatus.

The first reactor in the series is fed with two 65.6 weight percenthexenes, 29.6 weight percent TNPA, and 4.8 weight percent cyclooctanewhich serves as an internal standard for gas chromatography. Solution 2contains hexenes spiked with 38 ppm of Ni in the form of Ni octanoate(10 percent Ni in xylene). The volumetric flows of both solutions to thefirst flask are approximately equal so that the mole ratio of hexenes toTNPA is about 10.6 to 12.5 and the concentration of Ni between 20-23 ppmregardless of the overall feed rate. During feeding, the contents of allfour reactors are brought to reflux with stirring and the total volumeof all four reactors held constant at 110 cc by pumping out the contentsof the fourth reactor with the second peristaltic pump.

By varying the flow rates of the pumps, overall residence time of theliquid feed in the apparatus is varied between 23 and 65 minutes. Duringthese residence times, the TNPA reacts with the hexenes in the flasks toform tri-n-hexyl aluminum and propylene. The propylene is drivenoverhead by reflux and vented. The conversion of TNPA to tri-n-hexylaluminum of the effluent from the fourth reactor varies between 77 and89 percent.

The results of three runs (Examples 1-3) at steady state for the firstthree reactors are listed in Table 1. Steady state conversions for thefourth reactor are extrapolated in each case due to exhaustion of theTNPA supply when approximately 92 percent of theoretical response in thelast steady state was reached.

                  TABLE I                                                         ______________________________________                                        Result or                                                                     Condition      Example 1 Example 2 Example 3                                  ______________________________________                                        Absolute Conversion (%)                                                       Entering       13.7      13.7      13.7                                       Reactor 1      70        47        54                                         Reactor 2      85        65        71                                         Reactor 3      89        72        79                                         Reactor 4      90        77        80                                         Normalized Conversion (%)                                                     Entering       0         0         0                                          Reactor 1      65        40        46                                         Reactor 2      83        59        66                                         Reactor 3      88        68        74                                         Reactor 4      89        73        77                                         Temperatures (°C.)                                                     Reactor 1      69        67        68                                         Reactor 2      69        68        69                                         Reactor 3      69        68        68                                         Reactor 4      68        67        68                                         Theo. Approach to SS (%)                                                      Reactor 1      100.00    99.99     99.91                                      Reactor 2      99.95     99.99     99.31                                      Reactor 3      99.73     99.91     99.61                                      Reactor 4      98.99     99.61     92.12                                      Reactor Productivity (lb. Hexene/gal-hr)                                      Through Reactor 1                                                                            2.25      4.37      3.38                                       Through Reactor 2                                                                            1.42      3.25      2.42                                       Through Reactor 3                                                                            1.01      2.48      1.82                                       Through Reactor 4                                                                            0.76      2.00      1.41                                       Reactor vol. (mL)                                                             Total          110       110       110                                        Per Reactor    27.5      27.5      27.5                                       Times (min)                                                                   Total Res. Time                                                                              65        23        34                                         Res Time Per Reactor                                                                         16.2      5.8       8.6                                        Total Run Time 163       65        60                                         No. of Res. Times                                                                            2.5       2.8       1.8                                        Ni Conc. (ppm wt)                                                                            23        20        21                                         Hexene/TNPA Ratio                                                                            12.5      10.6      10.8                                       ______________________________________                                    

EXAMPLE 4

Reaction mass from Example 3 is continuously stripped to separate theinternal hexenes from aluminum alkyls as illustrated in the strippingportion of the flow diagram in FIG. 1.

Reaction mass is fed with a spared FMI positive displacement pumpthrough a 12-inch preheater jacketed with 100° C. 2-centistokepolyalphaolefin into the top of a vacuum-jacketed 19 mm 5-stageOldershaw Column. The flow rate is varied between 1.5 and 3.0 mL/min. Avoltage regulator on a 50 cc Glass-Coil heating mantle around thereboiler of the Oldershaw Column is set at 90 percent and cyclohexane isfed to the reboiler with a peristaltic pump at such a rate as tomaintain the reboiler bottoms temperature at 100° C., 125° C., or 150°C. The cyclohexane feed rates are 3.0, 1.5, and 0.6 mL/min.,respectively. The volume in the reboiler is maintained at 18 mL bycontinuously pumping out the stripped alkyls with a peristaltic pump.During this process, internal hexenes in the feed are stripped overheadand collected and stripped aluminum alkyl product collects in thereboiler.

The reboiler compositions are as follows:

    ______________________________________                                        Cyclohexane  Temperature                                                                              Internal Hexenes in                                   Rate (mL/min)                                                                              °C. Stripped Alkyl                                        ______________________________________                                        3.0          100        nil                                                   1.5          125        6.6%                                                  0.6          150        1.8%                                                  ______________________________________                                    

There is no evidence of decomposition to aluminum metal duringcontinuous stripping experiments.

This Example shows that it is possible to strip the product from Example3 in a continuous manner to remove most or all of the internal hexenesfrom the aluminum alkyl without decomposition to aluminum metal andwithout the application of vacuum. This is accomplished by use of astripping agent, in this case, cyclohexane, to provide stripping actionto remove the internal hexenes overhead. Use of a stripping agent alsoobviates the need to use excessive heat or vacuum to remove the hexenes.

EXAMPLES 5-7

A continuous isomerization/displacement is carried out using a singlestirred tank reactor which was similarly equipped to those used inExamples 1-3. The nickel catalyst (10 percent Ni 2-ethyl hexanoate inxylene) is pumped by a catalyst syringe pump to the internal hexene feedline and the internal hexene-catalyst mixture is continuously pumpedinto the reactor. Tri-n-propyl aluminum is also continuously pumped tothe reactor. Product aluminum alkyl is continuously removed from thereactor. The displaced propylene is removed at the top of the condenserand vented through a nitrogen purge line. Steady states are achieved ineach example. The catalyst concentration is varied from 18 to 101 ppmnickel. A summary of conditions and results is given in Table II. Inorder to allow the system to relax, 3.5 τ (residence time) are allowed.

                                      TABLE II                                    __________________________________________________________________________                               Residence                                                                           SS                                           Temp.    Ni   Flows (mL/min)                                                                         Molar                                                                             Time  Corrected                                    Example                                                                            (°C.)                                                                      Conc.                                                                              Hexene                                                                             TPA Ratio                                                                             (min) Conversion                                   __________________________________________________________________________    5    63° C.                                                                     201 ppm                                                                            2.13 0.33                                                                              9.2 13.7  50.8%                                        6    64° C.                                                                      18 ppm                                                                            2.10 0.33                                                                              8.9 12.8  40.1%                                        7    64° C.                                                                      38 ppm                                                                            2.10 0.33                                                                              8.9 12.8  45.3%                                        __________________________________________________________________________

In FIG. 2, an embodiment of the continuous back-displacement process forrecovering 1-alkenes from the aluminum alkyls prepared in theisomerization/displacement step using a catalyst is schematicallyillustrated. The illustrated embodiment employs a plug flow displacementreaction which is carried out in tubular reactor 71 which is equippedwith a jacket to provide temperature control such as by apolyalphaolefin (PAO) liquid bath. Stripped alkyl aluminum product fromtank 66 is fed to reactor 71 through lines 73 and 70 by metering pump72. The product is pretreated to remove any aluminum hydride formed inthe stripping step which would poison the catalyst. The 1-olefin for thedisplacement reaction is fed to reactor 71 through line 70 by meteringpump 75. The catalyst solution is fed from supply 76 to reactor 71through lines 77 and 70 by pump 78. The 1-olefin feed displaces theproduct 1-olefin in reactor 71 and the excess 1-olefin, the product1-olefin, and displaced alkyl aluminum exit from reactor 71 through line79. The excess displacing olefin and product 1-olefin are separated fromthe bottom stream containing the back-displaced alkyl aluminum which iscollected in tank 80. The product 1-olefin and excess olefin exitthrough line 81. The product 1-olefin is separated from the excessdisplacing olefin which can be recycled to the displacement reactor. Theback-displaced alkyl aluminum can be recycled to theisomerization/displacement reaction with a purge used to removedeactivated Ni catalyst impurities. When a lead kill is used todeactivate the catalyst after the reaction mixture exits from thedisplacement reactor, the nickel and lead are removed by filtration. Ina suitable system for a lead kill process, the lead solution andreaction mixture are fed to a mixing tee, the mixture is filtered andthen passed through a jacketed, packed tubular reactor prior toseparation of the olefins from the residual aluminum alkyl.

EXAMPLE 8

A continuous back-displacement process of 1-hexene from a hexylaluminumproduct was carried out as follows. The reaction mass from Example 4 wasupgraded with 1-hexene, (50/50 weight ratio), at gentle reflux, (70°C.), for one hour. The solution was allowed to cool and volatiles werepartially removed under vacuum for one hour. The solution was thenfurther stripped with a nitrogen purge overnight. Gas chromatographyanalysis of the upgraded stripped alkyl aluminum showed no internalhexenes and 0.3 percent residual 1-hexene based on hexyl groups and1-hexene. The alkyl aluminum was upgraded, according to this process, inorder to remove aluminum hydrides which would deactivate thedisplacement catalyst.

The resulting TNHA and liquid propylene were fed into the reactor viametering pumps. Nickel in the form of 10 percent by weight Ni octanoatein mineral spirits and nonane was fed to the reactor via a syringe pump.The reactor consisted of a 1/4 inch diameter stainless steel tube, 24inches in length, which was jacketed with a PAO bath to provide aconstant temperature o 25° C. The reaction solution was sampled directlyafter the reactor.

Flow rates were varied to achieve the following conditions:

    ______________________________________                                        Propylene/Aluminum =    6.7                                                   Alkyl mole ratio                                                              Residence time in reactor =                                                                           5.2 minutes                                           ppm Ni in reaction solution =                                                                         22                                                    ______________________________________                                    

The reactor and propylene feed tank were kept at a constant pressure of180 psi with a nitrogen blanket. All reactants were in the liquid phase.The reaction solution was sampled using a 6 port 2-way valve. The sampleloop was in line with the reactor or with the nitrogen/heptane purge.The sample loop was washed with heptane into the sample vial to insurethat all reactants were collected. The samples were immediatelyhydrolyzed with 2N HCl. A gas chromatograph run on the organic phase wasused to determine the percent conversion of hexyl groups to 1-hexene.

A 65 percent conversion of hexyl groups to 1-hexene resulted. There wereless than 0.5 percent by weight internal hexenes formed. This exampledemonstrates that the upgraded TNHA from Example 4 can undergoback-displacement with propylene and Ni catalyst to form very pure1-hexene and TNPA.

EXAMPLE 9

The back-displacement reaction was undertaken as in Example 8 except thereaction was run at atmospheric pressure, 1-octene was used as thedisplacing olefin and a lead kill was used to deactivate the catalystafter displacement. The nickel (TNHA) used was Ethyl TNHA which had beentreated with 1-hexene as described in Examples 1-3 under the heading"Treatment of Aluminum Alkyls" to remove aluminum hydride The TNHA feedconsisted of 300 grams of TNHA, 30 grams of cyclooctane to use as a gaschromatograph standard, and 10 grams of 1-octene to help cut theviscosity. The 1-octene feed consisted of 500 mL of 1-octene and 1 mL ofa 0.01284 gram Ni/mL of nonane solution. The Ni catalyst was 10 percentby weight Ni octanoate dissolved in mineral spirits. The Pb reagent usedwas 24% by weight Pb hexanoate in mineral spirits. The Pb solution wasdiluted with heptane to form a 0.1138 gram Pb/mL solution.

The 1-octene/Ni feed was pumped into the reactor via a metering pump.The TNHA feed was also fed into the reactor via a metering pump. Therewas an in line mixer right after the TNHA inlet to help insure goodmixing. The reactor was a 3/8 inch stainless steel tube which wasjacketed with a PAO bath. The tube was 15 inches long. The tube waspacked with 100 mesh glass beads to insure plug flow. The reactionsolution was sampled directly after leaving the back-displacementreactor. A 10 port 2-way valve was used which allowed for consistentsampling with heptane and nitrogen purge through the sample loop toinsure that all reactants were collected.

The reaction mixture was then fed to a 1/16 inch tee at which point thePb kill solution was added. The Pb solution was added via a syringepump. The reaction solution was filtered and then passed through a PAOjacketed 1/4 inch reaction tube. The tube was 24 inches long and waspacked with 100 mesh glass beads After passing through the Pb reactiontube, the reaction solution was sampled again using another 10 port2-way valve. The reaction solution was then collected in a 1-liter bomb.

Flow rates were set to achieve the following conditions:

    ______________________________________                                        TNHA =                 0.38 g/min                                             1-octene =             1.57 g/min                                             Mole ratio of =        11.9                                                   Olefin/Aluminum Alkyl                                                         Ni concentration =     29 ppm                                                 Pb concentration =     242 ppm                                                Mole ratio of Pb/Ni =  2.3                                                    ______________________________________                                    

After the back-displacement reaction the conversion of hexyl groups to1-hexene was 48.5 percent with a 1-hexene purity of 99.2 percent.

After the lead kill reaction the conversion was 57.9 percent with a1-hexene purity of 99.4 percent.

What is claimed is:
 1. A continuous process for preparing an alkylaluminum compound from an internal olefin, said process comprising:(a)continuously feeding (i) a linear internal olefin containing 4 to about30 carbon atoms or a mixture of such internal olefins, (ii) a trialkylaluminum, the mole ratio of said linear internal olefins to saidtrialkyl aluminum being about 1-50:1, and (iii) a catalytic amount of anisomerization catalyst to a reaction zone so as isomerize the internalolefinic double bond to form at least some linear 1-olefin whichdisplaces alkyl groups from said trialkyl aluminum and forms an alkylaluminum compound wherein at least one of the alkyl groups bound toaluminum is a linear alkyl derived from said linear 1-olefin, and (b)continuously removing olefin formed by the displaced alkyl groups andreaction mixture containing said alkyl aluminum compound from thereaction zone.
 2. The process according to claim 1 wherein said reactionzone is a single reactor.
 3. The process according to claim 1 whereinsaid reaction zone comprises a plurality of reactors in series.
 4. Theprocess according to claim 1 wherein said reaction zone comprises aplurality of stirred tank reactors in series.
 5. The process accordingto claim 4 wherein additional isomerization catalyst is fed to one ormore of the subsequent reactors.
 6. The process according to claim 1wherein said catalyst is an isomerization/displacement catalyst.
 7. Theprocess according to claim 4 wherein said catalyst is anisomerization/displacement catalyst.
 8. The process of claim 1 whereinsaid trialkyl aluminum contains less than about 1.0 weight percent ofaluminum hydride impurity and said catalyst is a nickel-containingisomerization/displacement catalyst.
 9. The process of claim 8 whereinthe nickel-containing catalyst is selected from nickel(II) salts,nickel(II) carboxylates, nickel(II) acetonates, nickel(0) complexes andmixtures thereof.
 10. The process of claim 9 wherein thenickel-containing catalyst is selected from nickelbis-1,5-cyclooctadiene, nickel acetate, nickel naphthenate, nickeloctanoate, nickel 2-ethylhexanoate and nickel chloride
 11. The processof claim 8, wherein said catalyst is present in an amount of from about0.01 to 5.0 mole percent of the trialkyl aluminum, said linear internalolefin is an n-hexene, and said trialkyl aluminum istri-n-propylaluminum.
 12. The process of claim 11 wherein said catalystis nickel octanoate nickel acetate, nickel naphthenate, or nickel2-ethylhexanoate.
 13. The process of claim 4 wherein said trialkylaluminum contains less than about 1.0 weight percent of aluminum hydrideimpurity and said catalyst is a nickel-containingisomerization/displacement catalyst.
 14. The process of claim 13 whereinthe nickel-containing catalyst is selected from nickel(II) salts,nickel(II) carboxylates, nickel(II) acetonates, nickel(0) complexes andmixtures thereof.
 15. The process of claim 14 wherein thenickel-containing catalyst is selected from nickelbis-1,5-cyclooctadiene, nickel acetate, nickel naphthenate, nickeloctanoate, nickel 2-ethylhexanoate and nickel chloride.
 16. The processof claim 13 wherein said catalyst is present in an amount of from about0.01 to 5.0 mole percent of the trialkyl aluminum, said linear internalolefin is an n-hexene, and said trialkyl aluminum istri-n-propylaluminum.
 17. The process of claim 16 wherein said catalystis nickel octanoate, nickel acetate, nickel naphthenate or nickel2-ethylhexanoate.